1. Field of the Invention
The present invention relates to a process for determining the speed of linear or rotational movement of a member producing pulses whose frequency is proportional to this speed and the device for implementing said process.
2. Description of the Prior Art
Devices are known in which, on the one hand, movement is measured by counting pulses produced by a sensor and, on the other hand, the time by recording, in a second counter, the pulses of a rapid clock. Such a device is described in French Pat. No. 2,420,767.
However, the device described in French Pat. No. 2,420,767 has the drawback of requiring a second clock, called slow clock, for generating a time interval during which the pulses from the sensor and the pulses from the clock are counted. Another disadvantage of the device is the need to synchronize the whole of the device to the rapid clock.
Finally, it has been discovered that, when the frequency of the rapid clock and the frequency of the slow clock have been fixed, the device can only operate correctly in a restricted frequency range of the pulses from the sensor, said range being in any case less than the frequency of the rapid clock.
Furthermore, the slow clock frequency also limits the operating range of the sensor in the low frequencies.
This is all the more true since, in French Pat. No. 2,420,767, a circuit is provided for determining whether the frequency of the pulses from the sensor is lower than that of the slow clock and, in this case, initiating the calculations solely on the appearance of the pulses from the sensor.
Similarly, in the article by S. BEDERMAN, from IBM T.D.B., volume 13, no. 4, September 70, pages 1017 to 1018, a device is described in which the time measuring counter 19 is reset by the pulses from the sensor, which thus compels the sensor to operate at frequencies less than the frequency of the time measuring clock. Moreover, the interruptions which cause transfer of the contents from the counters into registers are not correlated with the pulses of the sensor and of the clock. That risks causing sensor or clock pulses to be lost and requires additional registers for taking the current time into account.